It begins in the morning. The victim awakens feeling unwell. They’re without appetite. Their head aches. Sore throat. Fever. Chills.

What’s happening to the victim’s body isn’t dissimilar to other diseases that attack the immune system, but this one’s substantially more aggressive. “Exactly when and where you caught Ebola virus is unclear,” wrote Lancaster University lecturer Derek Gatherer. “It can take anywhere between two and 21 days from initial infection to the first symptoms. What is more certain is that you are now infectious yourself. Your family, friends and anyone in close contact with you are now in mortal danger.”

The danger has never been greater in West Africa as the worst Ebola outbreak on record continues its deadly sweep of jungles and cities, hopping national borders and frustrating hundreds of doctors who parachuted in to vanquish the disease but have so far failed. As of Thursday, the pandemic with a 90 percent mortality rate has afflicted at least 635 people and killed more than 367 of them in Liberia, Sierra Leone and Guinea, where it is believed to have begun.

The toll is greater than the 280 dead in 1976, when the virus was first identified near the Ebola River in what is now the Democratic Republic of Congo.

Earlier this week, Doctors Without Borders said the situation was unprecedented. “The epidemic is out of control,” Bart Janssens, the director of operations, said. “We have reached our limits. Despite the human resources and equipment deployed by [Doctors Without Borders] in the three affected countries, we are no longer able to send teams to the new outbreak sites.”

Staff of Doctors without Borders carrying the body of a person killed by viral hemorrhagic fever at a center for victims of the Ebola virus in Guekedou, Guinea, on April 1, 2014. (AFP)

Now the World Health Organization is urging “drastic action” to try and stop the outbreak. It warned Friday that nations near those hit by the Ebola epidemic should prepare for the possible arrival of travellers carrying the virus.

“We want other countries in West Africa to be ready – bordering countries, Ivory Coast, Mali, Senegal, Guinea Bissau – to prepare themselves in case people affected with the disease may be also travelling,” WHO medical officer Dr. Pierre Formenty told a briefing in Geneva.

WHO is “gravely concerned [by] the ongoing cross-border transmission into neighboring countries as well as the potential for further international spread,” regional doctor for Africa, Luis Sambo, told the Guardian. “This is no longer a country specific outbreak but a sub-regional crisis that requires firm action by governments and partners.”

Misinformation, lack of education and an underestimation of the severity of the outbreak have all contributed to what is quickly becoming an international crisis. “At the end of April, we started to see a decrease in the number of cases and we maybe saw a relaxation by the teams in the three countries, and this relaxation allowed things to restart,” Janssens said.

One of the major problems: funerals. People are continuing to attend funerals of the dead, despite warnings and regardless of safety measures. Then a few days or weeks later, the attendants themselves wake up feeling unwell, without an appetite and feverish.

Then Ebola escalates, wrote Gatherer, with the onset of “chronic abdominal pain. The fever intensifies and you start to vomit and develop diarrhea.” After that, the disease will either do two things. Release the victim from its grasp, or “progress to the horrors of ‘cytokine storm.'”

What’s “cytokine storm?” It’s the “convulsion of your ravaged immune system that will plunge you into the terminal phase of Ebola virus disease known as hemorrhagic fever,” Gatherer wrote in the Conversation.

At this point, the victim’s immune system will assail every organ in the body, and the victim will slowly bleed to death as blood vessels burst everywhere. The eyes will turn crimson. His or her vomit will be stained red. “And large blood blisters develop under your skin,” Gatherer wrote. “You are now at the peak of infectiousness as Ebola virus particles, read to find their next victim, pour out of your body along with your blood.”

Such education about the disease hasn’t penetrated some communities, doctors say. The Sierra Leone government tried with a fact sheet that tells people to refrain from eating “bush meats” and that a mixture of ginger, honey, garlic, onion and vinegar cannot cure Ebola. “Is it true that drinking alcohol prevents Ebola? Is it true that Ebola is a curse?” the fact sheet asked. “No, it is not true.”

Distrust of medical professionals in some communities has made it difficult to ensure compliance with health precautions. “States are getting better but the problems of communication continue,” Pierre Formenty, a WHO specialist, told Agence France-Presse. “The medical corps on their own cannot stop this epidemic. It is only with the help of the population that we can fight this epidemic and stop it.”

The WHO has announced an 11-nation meeting in early July to address the outbreak and “discuss the best way of talking the crisis collectively.”

Correction: An earlier version of this story overstated the total number of afflicted persons reported by the World Health Organization. The number is 635, of whom 367 have died.